Carburization of A-106B Tubes
Carburization of A-106B Tubes
(OP)
We have a lean oil heating furnace with A-106b tubes. The approximate tube temperature (surface) is 750F. We have a haz-op item on this that says we need to verify that the tubes are not susceptible to carburization. Can someone lead me to a reference chart, or some other text to help me verify this. Thanks.





RE: Carburization of A-106B Tubes
RE: Carburization of A-106B Tubes
Carburized surfaces have diffused carbon enrichment at the surface which makes the surface a higher carbon alloy and allows local hardening. This would not occur at 750F.
AEF surmises you mean "graphitization", which is a slow process converting carbon in the pearlite from an iron carbide to the graphitic form of carbon and weakening the steel. This also is so slow at 750F it is a non-issue. You can test for it metallurgically with in-field metallography/replication or by destructive testing of removed samples - welds are usually selected. The main message you should sell is that this normally is not necessary at 750F